Effects of surface heating on precipitation over the Tibetan Plateau and its eastern margin

Abstract

The high terrain of the Tibetan Plateau (TP) has a very important impact on the weather and climate of China, East Asia, South Asia, and even the Northern Hemisphere. However, in recent years, the reasons for the decrease in precipitation in the southeastern edge of the plateau have resulted in cutting-edge research regarding the impact of the TP and its surrounding areas on downstream weather and climate. In this study, the spatial and temporal distribution of surface heat flux and precipitation were analyzed from 1998 to 2022, and the possible mechanism of the decrease of precipitation in the eastern edge of the plateau is explored. The main conclusions are as follows: The annual average sensible heat flux in the TP and its east side is positive, with an average of 33.73 W/m². The annual average latent heat flux is positive, with an average of 42.71 W/m². Precipitation has a similar annual average and seasonal distribution, with modest amounts in the northwest and substantial amounts in the southeast. The average annual accumulated precipitation is 670.69 mm. The first mode of the Empirical Orthogonal Function (EOF) shows that sensible heat flux decreases first, then increases, and then finally decreases during 1998–2022. The modes show the opposite trend in middle part of the plateau. The latent heat flux initially decreases, then increases, and finally decreases in the western plateau and near Sichuan Basin. The mode, however, displays the opposite tendency throughout the rest of the region. The precipitation in the north and south sides of the plateau has decreased since 2013, which is consistent with the changing trend of sensible heat flux. In the rest of the region, the change trend is not obvious. The sensible heat of the main body of the plateau and its east side and Sichuan Basin is negatively correlated with precipitation, that is, when sensible heat flux of the main body of the plateau and its east side and Sichuan Basin is more (less), local precipitation is less (more). The latent heat of the main body of the plateau and its east side, Sichuan Basin is positively correlated with precipitation, indicating that when latent heat flux of the main body of the plateau and its east side, Sichuan Basin is more (less), local precipitation is more (less).